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Characterization and effects of thermal cycling on the properties of paraffin/expanded graphite composites

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journal contribution
posted on 23.09.2019 by Qingqing Wang, Dan Zhou, Yuming Chen, Philip Eames, Zhigen Wu
Paraffin has been one of the most potential phase change materials (PCMs) in low-temperature latent heat storage. However, the low thermal conductivity of paraffin restricts its thermal performance and limits its large-scale applications. Adding a suitable proportion of expanded graphite (EG) into the paraffin can enhance the heat transfer rate, thus improve the thermal efficiency of the whole heat storage system. In this paper, five paraffin/EG composites with 2 wt%, 5 wt%, 10 wt%, 15 wt% and 20 wt% of EG were prepared to study their long-term characteristics. Effects of thermal cycling (up to 100 thermal cycles) on the thermophysical properties were studied, such as, phase transition temperature, latent heat, chemical compatibility, thermal stability and thermal conductivity. The paraffin/EG composite has the potential for converting intermittent electricity directly into heat, therefore, the effect of thermal cycling on electrical conductivity was also studied. The results showed that both phase transition temperature and latent heat decreased slightly after 100 thermal cycles, within 1% and 3% respectively. Thermal cycling changed the distribution and interaction between the paraffin and EG resulting in a lower temperature thermal decomposition process. Long-term thermal cycling also had a more negative effect on the increase rate in thermal and electrical conductivity achieved for higher EG content.

Funding

National Natural Science Foundation of China (No.51106112, 51676141), the Fundamental Research Funds for the Central Universities and the Engineering and Physical Sciences Research Council (EPSRC) through Grant reference EP/K011847/1, Interdisciplinary Centre for Storage, Transformation and Upgrading of Thermal Energy (i-STUTE)

History

School

  • Mechanical, Electrical and Manufacturing Engineering

Published in

Renewable Energy

Volume

147

Issue

Part 1

Pages

1131 - 1138

Publisher

Elsevier

Version

VoR (Version of Record)

Rights holder

The Authors

Acceptance date

17/09/2019

Publication date

2019-09-18

Copyright date

2019

ISSN

0960-1481

Language

en

Depositor

Dr Dan Zhou

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